Spring arrangement apparatus for mounting a vibration-sensitive or shock-sensitive device

ABSTRACT

Spring arrangement for mounting a vibration- or shock-sensitive device attached to a supporting member in a housing, with the supporting member being fastened to the housing by helical spring elements. The supporting member is suspended in the housing by helical spring elements so that each elastic force component of one spring applied to the supporting member in a specific direction is counteracted by at least one elastic force component of another spring applied in the opposite direction so that the supporting member remains approximately in the center of the vibration clearance provided regardless of the position in which the housing is mounted in a motor vehicle. Due to the opposing elastic forces of the springs, the spring constant and therefore the natural frequency of the overall system can be advantageously increased, thus avoiding undesired points of resonance at low frequencies.

BACKGROUND INFORMATION

A method for attaching a vibration- or shock-sensitive device, such as astereo system, compact disc player, CD changer, or floppy or hard diskdrive to a supporting member and mounting the supporting member withvibration damping in a housing via helical spring elements is alreadyknown. Particularly in motor vehicles, low-vibration and low-impactmethods of attaching compact disc players are required in order tooperate the equipment without interference. For this purpose, the deviceis thus elastically suspended on the equipment housing, which ispermanently installed in the motor vehicle, with the supporting memberbeing attached to the housing via multiple helical spring elementsprovided in the form of either extension springs or compression springs.

FIG. 1a shows a conventional spring arrangement using extension springs,and FIG. 1b shows the arrangement using compression springs. In FIG. 1a,a supporting member 2 in the form of a plate, with a compact disc player1, for example, attached to its top, is fastened to the top of a cuboidhousing 3 via a total of four helical springs (10, 11), only two ofwhich are illustrated. According to this arrangement, an excitationacting upon housing 3 produces only an extremely diminished accelerationof CD player 1. By suspending the device in this manner, points ofresonance form which are associated with an undesirable, strongvibration of device 1 at low excitation frequencies, thus causing device1 to bump against housing 3. To avoid this disadvantage, it is desirableto increase natural frequency w_(max) of the system subject tovibrations, since this will considerably diminish the acceleration of CDplayer 1 during excitation. With a given mass M according to equation(1), this can be achieved only by increasing spring constant K.$\begin{matrix}{\omega_{\max} = \sqrt{\frac{K}{M}}} & (1)\end{matrix}$

However, the supporting plate suspended on springs 10, 11 in FIG. 1amust be displaced by the force of its own weight until it ends up moreor less in the center of the vibration clearance provided for it, theheight of which is marked x in FIG. 1a. This can be achieved by reducingthe spring constant, which, however, should be avoided as shown byequation (1), due to the resulting undesired reduction in the naturalfrequency. The spring arrangements illustrated in FIG. 1a and FIG. 1balso have the disadvantage that they can be used only in situationswhere the springs are loaded axially, i.e., in the direction of thespring axis. However, the springs are more compliant when the force isapplied radially. The springs are barely extended in that case, butrather are merely swivelled or bent. As a result, only weak restoringforces are applied in the radial direction. Radially oriented forces actupon the springs when the device is installed in the motor vehicle in adirection other than the specified mounting position. A situation ofthis type is illustrated in FIG. 2a. When device 3 tilts to the side,supporting member 2 is displaced far to the side by its weight, thusreducing the vibration clearance. If a vibration or impact excitationoccurs, there is the danger of the device striking the side walls of thehousing. The use of a spring arrangement, like the one shown in FIG. 1,is therefore limited to situations in which the compact disc player isspecifically designed for a predetermined mounting position, e.g., if itcan be installed in the vehicle only horizontally or only vertically.Compact disc players in car radio equipment often need to be installedin consoles at an angle. If the player housing is attached to the roofstructure of a bus, for example, a certain angle of inclination isdesirable in order to make the CDs easier to insert. According to therelated art, supporting member 2 is attached to housing 3 in suchsituations, using an additional spring 19 that is adjusted to the angleof inclination. This also has the disadvantage that the CD player can beinstalled in no position in the vehicle other than the predeterminedone. That is why some devices include an adapter mechanism which can beused, for example, to adjust a CD changer to the mounting position athand within certain limits. The known related art is illustrated in FIG.7a and FIG. 7b. FIG. 7a shows the device with its housing 3, initiallymounted in a horizontal position. The CD changer (not illustrated) isattached to a supporting member 2 that is suspended on two discs 40 viatwo springs 10 and 11 so that supporting member 2 is located more orless in the center of the vibration clearance provided for it. Discs 40are each attached to the side walls of device housing 3 so that they canrotate around an axis 41. If the device is installed in a horizontalposition, springs 10 and 11 are located in position A in FIG. 7b. If thesame device is now installed in a vertical position in the motorvehicle, housing 3 is first rotated 90 degrees, and the two discs 40 arerotated 90 degrees in the opposite direction on actuating element 42until springs 10 and 11 are in position B shown in FIG. 7b andsubsequently locked in place. The elastic force of springs 10 and 11compensates for the weight of supporting member 2, along with the devicearranged upon it, so that the supporting member can also vibrate freelyin the housing even when mounted in a vertical position. Anyintermediate positions between 0 and 90 degrees can also be set. Thedisadvantage of this related art is that it requires an expensiveadapter mechanism, which increases the device production costs. Arelatively complicated adjustment of the adapter mechanism to thedifferent mounting positions is also necessary, making it possible toincline the device only around an axis that runs parallel to axes 41.

SUMMARY OF THE INVENTION

The spring arrangement according to the present invention has theadvantage that both the spring constants of the individual springs andthe natural frequency of the system can be increased. This is achievedby mounting the supporting member in a predetermined position in thehousing. A component of elastic force applied in a specific direction isthen always counteracted by a component of elastic force in the oppositedirection. This prevents the springs from lifting or lowering thesupporting member too far away from the center of the preset vibrationclearance when using very rigid extension springs or compressionsprings. At the same time, the supporting member can be installed indifferent positions in a motor vehicle without having to adjust thespring arrangement or use an adapter mechanism. Another advantage isthat the position of the supporting member relative to the housingvaries only slightly in different mounting positions, allowing thedevice to be operated without interference independently of the mountingposition when vibrations or shocks occur.

This is essentially achieved by the fact that the springs not onlyswivel or bend when the housing tilts or rotates, as in the case of therelated art illustrated in FIG. 2a, but rather that, with the springarrangement according to the present invention, the supporting member ismounted in such a way in the housing that the springs are extended whenthe supporting member is displaced in any direction. As a result,restoring forces always counteract the displacement.

For example, the spring arrangement is advantageously designed so thatthe supporting member is arranged more or less in the center of thevibration clearance. This prevents the device from bumping against thehousing at high oscillation amplitudes.

A further advantage is the use of inexpensive extension springs, theends of which can be easily attached to the supporting member andhousing and then released again, since this reduces the amount ofinstallation work needed, making it cost-effective.

A further advantage is to design the supporting member in the form of aflat, rectangular supporting plate. The rectangular supporting plate canbe advantageously mounted in a cuboid housing using springs provided inthe corner areas.

A further advantage is provided by mounting the supporting plate in thehousing using four extension springs projecting from the plate top andbottom, since this provides stable, elastic mounting of the supportingplate in the center of the vibration clearance and parallel to the upperand lower housing walls.

If the supporting plate is attached to the upper housing wall by twoextension springs in two diagonally facing corner areas of its top andto the lower housing wall by two springs projecting from its bottom,four springs are sufficient in order to mount the supporting plateelastically in the housing. This can reduce the production costs.

A particular advantage is provided by mounting the supporting plate inthe housing with extension springs projecting at an angle from the plateand facing away from it. This allows the springs to extend even farther,with the resulting restoring forces being even stronger, when the deviceis mounted in an inclined position.

If the supporting plate is attached to the housing by extension springsthat are fastened to the longitudinal sides of the supporting plate andoriented more or less parallel to it, an arrangement with three springspositioned on same plane as the supporting plate is sufficient.

In some situations, e.g., in the case of a CD changer, thevibration-sensitive device is attached to a cuboid supporting member. Insuch situations, the cuboid supporting member is advantageouslysuspended between two opposite side walls of the housing using twotapered springs. The first and last coils of the tapered spring do notcontribute to spring compliance and are advantageously firmly attachedto the side walls in an attachment area lying flat against the sidewalls. The tapered springs allow the supporting member to be mounted inthe housing in a manner that is particularly space-saving andeconomical.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a shows a conventional spring arrangement with a supporting membersuspended on extension springs.

FIG. 1b shows another conventional spring arrangement with thesupporting member being mounted on compression springs.

FIG. 2a shows the spring arrangement shown in FIG. 1a in which thedevice housing is tilted.

FIG. 2b shows the spring arrangement shown in FIG. 2a with an additionalspring adjusted to the tilting angle.

FIG. 3 shows a first exemplary embodiment of the spring arrangementaccording to the present invention for a compact disc player.

FIG. 4a shows a second exemplary embodiment with springs facing awayfrom the supporting plate at an angle.

FIG. 4b shows a diagram of forces for the embodiment illustrated in FIG.4a.

FIG. 4c shows a third embodiment with a leg integrally molded onto thesupporting plate.

FIG. 5 shoes an exemplary embodiment of the spring arrangement accordingto the present invention with four springs.

FIG. 6 shows a further embodiment according to the present inventionwith three springs.

FIG. 7a shows a schematic cross-section of a conventional CD changersuspended on two springs.

FIG. 7b shows a side view of the CD changer show in FIG. 7a.

FIG. 8a shows a schematic cross-section of an exemplary embodimentaccording to the present invention of the spring arrangement for a CDchanger.

FIG. 8b shows a side view of the spring arrangement show in FIG. 8a.

DETAILED DESCRIPTION

FIG. 3 shows a first embodiment of the spring arrangement according tothe present invention. Vibration- or shock-sensitive device 1 in theembodiment illustrated here is a compact disc player. Compact discplayer 1 is located on top 25 of a rectangular supporting plate 2.Supporting plate 2 is attached to top 27 of a cuboid housing 3 by fourhelical spring elements, only two of which are illustrated in FIG. 3,e.g., springs 10 and 11. Housing 3 is, in this case, shown in ahorizontal mounting position. Inexpensive extension springs made of wirecoiled in a spiral shape, with ends designed in the form of eyes, areused as the helical spring elements. The extension springs allowsupporting plate 2 to be easily installed and removed. The extensionspring eyes are attached to hooks provided in the corner areas ofrectangular supporting plate 2 not covered by CD player 1 and to hookson housing top 27 opposite the first hooks. Bottom 26 of supportingplate 2 is attached in the same manner to housing bottom 28 via fouradditional springs, of which only springs 12 and 13 are illustrated inFIG. 3. The length of the extension springs is selected so that allextension springs attached to housing 3 must extend when they arefastened to the hooks positioned on supporting member 2. After all eightsprings have been attached, supporting plate 2 is mounted in housing 3.The tensile force of spring 10 applied perpendicular to supporting plate2 is counteracted by the tensile force of spring 12, the tensile forceof spring 11 is counteracted by the tensile force of spring 13, etc.Because the spring constant is chosen so that the force with whichsprings 10, 11 provided on the plate top pull the supporting platetoward housing top 27 is the same as the force with which oppositesprings 12, 13 provided on plate bottom 26 pull supporting plate 2toward housing bottom 28, the spring constants, and thus the overallrigidity of the oscillatory system, can be increased without displacingthe supporting plate from the center of the vibration clearance. Thisadvantageously pushes the natural frequency of the overall system towardhigher frequencies. Supporting plate 2 can be connected to housing 3 notonly by the spring elements but also by vibration dampers, which are notillustrated in FIG. 3.

Furthermore, the weight of supporting plate 2 and device 1 causes only aslight extension of upper springs 10, 11 and a slight compression oflower springs 12, 13 with a greater spring constant. In the embodimentshown in FIG. 5, therefore, the distance from supporting plate 2 tohousing top 27 is slightly greater than the distance to housing bottom28. By slightly varying the spring length or adjusting the points atwhich the springs are attached to the housing sections, it is possibleto position supporting plate 2 exactly in the center of free vibrationexcursion x, with the plate oriented horizontally at an equal distancefrom housing top 27 and housing bottom 28.

By mounting housing 3 in an inclined position instead of the horizontalposition shown in FIG. 3, supporting plate 2 is displaced parallel tohousing bottom 28 by one component of its weight. The displacing weightforce acts on springs 10, 11, 12, 13 in the form of a radial force. Thisis the situation illustrated for the related art in FIG. 2a in whichsprings 10, 11 swivel or bend. In the spring arrangement according tothe present invention illustrated in FIG. 3, however, spring 12 preventsspring 10 from merely swiveling, spring 13 prevents spring 11 frommerely swiveling, etc. Because supporting member 2 is mounted in thecenter of the vibration clearance, all eight springs must extend whenhousing 3 tilts and supporting member 2 is displaced laterally. Thisextension, in turn, produces a restoring force which counteracts thelateral displacement and increases with the spring constant. The lateraldisplacement is thus much less pronounced than in the related art. Thearrangement also advantageously prevents supporting member 2 frombumping against the side walls of housing 3 under vibrational load orshocks.

FIG. 4a shows an exemplary embodiment illustrated in FIG. 3. The eightextension springs, of which only four springs 10, 11, 12, 13 facing theobserver are shown, project out at an angle from plate top 25 and bottom26 when device 3 is mounted in a horizontal position. The ends of theextension springs not attached to the corner areas of rectangularsupporting plate 2 are fastened to the eight corresponding corners ofcuboid housing 3. This is shown somewhat more clearly in thethree-dimensional representation of FIG. 5, which, however, illustratesonly four springs. It is, of course, also possible to attach the springsto the side walls or fixing elements of a frame instead of directly tothe corners of housing 3. Likewise, it is possible to provide fastenersin the housing and to attach some springs to the fasteners and othersprings to the housing walls. The important thing is only that thesprings are positioned at an angle toward the outside, with the elasticforce component of one spring applied in a specific direction beingcounteracted by an equally strong elastic force component of at leastone other spring. FIG. 4b shows a simplified diagram of forces for theembodiment illustrated in FIG. 4a. To make things simple, therepresentation here is limited to a two-dimensional view. Elastic forcesF₁, F₂, F₃, and F₄ act upon supporting plate 2. Each of these elasticforces, e.g., elastic force F₁, can be broken down into a horizontalcomponent F₁′ and a vertical component F₁″, which is counteracted by anelastic force component of another spring applied in the oppositedirection. For example, component F₁ is counteracted by component F₄′ ofspring 12, and component F₁″ is counteracted by component F₂″ of spring11. Because all forces applied compensate for each other, supportingmember 2 is positioned in the center of the vibration clearance. Theweight of supporting plate 2, which is relatively small compared to thespring forces, merely causes the supporting plate to be slightlydisplaced in the direction of housing bottom 28. The particularadvantage of this embodiment, compared to the example shown in FIG. 3,lies in the fact that the eight springs are pre-tensioned not only inthe horizontal direction, but in the vertical direction as well. Ifhousing 3 is mounted at an angle or even vertically, the inclinedsprings are therefore displaced farther in the axial direction than theyare in the example shown in FIG. 3, which results in stronger restoringforces. In the embodiment shown in FIG. 4a, equally strong restoringforces counteract the displacement of supporting member 2 in anydirection regardless of the mounting position.

FIG. 4c shows a further embodiment of the present invention. Supportingmember 2 in this case is formed by a rectangular plate 2 with a leg 20integrally molded onto longitudinal side 22 of the plate and projectingvertically from its bottom 26. Supporting plate 2 is mounted in housing3 by eight springs, of which only springs 10, 11, 12, and 13 are shownin FIG. 4c. The embodiment differs from the example shown in FIG. 4a bythe fact that spring 10 is not attached to top 25 of the supportingplate, but rather to end 29 of leg 20 projecting in the direction ofhousing bottom 28, and spring 12 is fastened to edge 22 formed by leg 20and supporting plate 2, so that springs 10 and 11 project above top 25of supporting member 2, while springs 12 and 13 project in the oppositedirection above bottom 26.

FIG. 5 shows an exemplary embodiment illustrated in FIG. 4a in whichsupporting member 2 is mounted in housing 3 by only four extensionsprings 10, 13, 14, 15. Springs 10 and 15 are attached to the supportingplate in two diagonally facing corner areas of supporting plate 2.Springs 10, 15 project outward at an angle from plate top 25 and areattached to housing 3 by their other ends in two corners diagonallyfacing top 27 of housing 3. The other two corner areas of supportingplate 2 are attached in the same manner to two other diagonally facingcorners on bottom 28 of housing 3 via springs 13 and 14. The springarrangement shown in FIG. 5 is therefore based on the spring arrangementin FIG. 4a described above in that four springs are alternately removedfrom top 25 and bottom 26. However, since restoring forces counteractany displacement of the supporting plate, regardless of the mountingposition, the spring arrangement in FIG. 5 has the advantage that itrequires only four springs.

FIG. 6 shows a further embodiment of the present invention whichrequires only three springs. Supporting member 2 is suspended like atrampoline in the center of cuboid housing 3 and attached to housing 3by three extension springs 16, 17, 18 arranged on the same plane assupporting plate 2. Extension spring 16 in the corner area formed bylongitudinal sides 21 and 24 of the supporting plate is attached to theinner edge of housing 2 opposite this corner area. In the corner areaformed by longitudinal sides 21 and 24, extension spring 17 is attachedto an adjacent inner edge of housing 3. Third extension spring 18connects the central portion of longitudinal side 23 opposite springs 16and 17 to the center of the housing wall located opposite the inneredges connected to springs 16 and 17. In the embodiment shown in FIG. 6,the distance from supporting plate 2 to the side walls of housing 3 mustbe slightly greater than in the example shown in FIG. 5.

FIG. 8a and FIG. 8b show a further embodiment of the present invention.In this case, the vibration-sensitive device (not illustrated) is a CDchanger that is positioned in a cuboid supporting member 2. Supportingmember 2 has at least two side walls 6 and 7 that are connected tohousing 3 by helical spring elements 10 and 11. Used as helical springelements 10, 11 are conventional tapered springs whose inner coils fittogether in a spiral shape when the spring is fully compressed, so thatthe height of the spring, in this case, equals the diameter of a singlecoil. The advantage of tapered springs is that they have a low overallheight. Tapered springs can be designed as wire or flat spiral springs.In addition, springs 10 and 11 can be provided as extension orcompression springs. In the embodiment shown in FIGS. 4a-c, springs 10,11 are designed as extension springs. The springs have, at their ends,two dummy coils 30 and 31 which do not contribute to spring compliance.End coil 30 of spring 10 is integrally attached to side wall 7 ofsupporting member 2 in an attachment area 33 lying flat against sidewall 7. End coil 31, which has the largest diameter, is integrallyattached to opposite side wall 46 of housing 3 in an attachment area 34.Spring 11 is attached in the same manner to side wall 6 of thesupporting member and to side wall 45 opposite side wall 46 of housing3. In an arrangement with only two springs, the attachment method causesrestoring forces to counteract peripheral forces which result whensupporting member 2 rotates around the axes of springs 10, 11 andproduces torsion in springs 10, 11. The tensile force of spring 10 isalso counteracted by the tensile force of spring 11 so that supportingmember 2 is suspended between tapered springs 10 and 11 approximately inthe center of the vibration clearance provided for it. A high enoughspring constant of the two springs is selected so that the weight ofsupporting member 2, along with the CD changer, produces only a veryslight vertical displacement of supporting member 2. If housing 3rotates around an axis that runs through the longitudinal axis ofsprings 10 and 11, equally strong restoring forces therefore alwayscounteract the weight of supporting member 2, due to the rotationalsymmetry of the tapered springs. In the case of a rotation around anaxis running perpendicularly to the paper plane in FIG. 8a, strongrestoring forces also counteract the horizontal displacement ofsupporting member 2, unlike the related art illustrated in FIG. 7a, sothat supporting member 2 continues to remain more or less in the centerof the vibration clearance.

What is claimed is:
 1. A spring arrangement apparatus for mounting at least one of a vibration-sensitive device and a shock-sensitive device, the apparatus comprising: a supporting plate, the supporting plate including a top portion and a bottom portion; a housing, the housing enclosing the supporting plate; and a spring arrangement, the spring arrangement consisting of: four helical spring elements including two first extension springs and two second extension springs, the spring elements suspending the supporting plate in the housing to provide a first elastic force component of one of the spring elements and at least one second elastic force component of another one of the spring elements, the first elastic force component being counteracted by the at least one second elastic force component, the first elastic force component being in a first direction, the at least one second elastic force component being in a second direction which is opposite to the first direction, wherein one of the first extension springs is situated in a first area of the supporting plate and another one of the first extension springs is situated in a second area of the supporting plate, the first area being diagonally opposite to the second area, wherein one of the second extension springs is situated in a third area of the supporting plate and another one of the second extension springs is situated in a fourth area of the supporting plate, the third area being diagonally opposite to the fourth area, wherein the first extension springs project from the top portion and are attached to at least one first section of the housing, the second extension springs projecting from the bottom portion and being attached to at least one second section of the housing which is situated opposite to the at least one first section, and wherein the spring elements maintain the supporting plate at a first distance from the at least one first section and at a second distance from the at least one second section, the first distance being substantially equal to the second distance; wherein the at least one of a vibration-sensitive device and a shock-sensitive device is enclosed within the housing when mounted on the supporting plate.
 2. The spring arrangement apparatus according to claim 1, wherein the supporting plate is situated approximately in a center of a vibration clearance, the vibration clearance being provided for the supporting plate.
 3. The spring arrangement apparatus according to claim 1, wherein the supporting plate is attached to the housing via the spring elements, the spring elements projecting at an angle from the supporting plate and facing away from the supporting plate.
 4. The spring arrangement apparatus according to claim 1, wherein: the supporting plate is rectangular, the supporting plate having a first corner, a second corner, a third corner and a fourth corner; the first area corresponds to the first corner, the second area corresponds to the second corner, the third area corresponds to the third corner, and the fourth area corresponds to the fourth corner; and the first corner is diagonally opposite from the second corner and the third corner is diagonally opposite from the fourth corner.
 5. The spring arrangement apparatus according to claim 1, wherein the first area, the second area, the third area, and the fourth area define a supporting plate plane.
 6. The spring arrangement apparatus according to claim 5, wherein the first extension springs extend from a top of the supporting plate plane and the second extension springs extend from a bottom of the supporting plate plane.
 7. The spring arrangement apparatus according to claim 5, wherein: a first two attachment points on the housing for the first extension springs lie within a first housing plane; and a second two attachment points on the housing for the second extension springs lie within a second housing plane, wherein the first housing plane is different from the second housing plane.
 8. A spring arrangement apparatus for mounting at least one of a vibration-sensitive device and a shock-sensitive device, the apparatus comprising: a supporting member, the supporting member including a top portion and a bottom portion; a housing, the housing enclosing the supporting member; and a spring arrangement, the spring arrangement comprising: helical spring elements including at least two tapered springs, the spring elements suspending the supporting member in the housing to provide a first elastic force component of one of the spring elements and at least one second elastic force component of another one of the spring elements, the first elastic force component being counteracted by the at least one second elastic force component, the first elastic force component being in a first direction, the at least one second elastic force component being in a second direction which is opposite to the first direction, wherein a first tapered spring of the least two tapered springs acts in a third direction, a second tapered spring of the at least two tapered springs acting in a fourth direction which is opposite to the third direction, wherein a first end of each of the spring elements is attached to a first side wall of the supporting member, a second end of each of the spring elements being attached to a second side wall of the housing, and wherein end coils of the at least two tapered springs include dummy coils which do not contribute to a spring compliance, a first end coil of the end coils being connected to the first side wall and a second end coil of the end coils being connected to the second side wall in lying-flat attachment areas. 